How To Prevent Bulging Corners on a 3D Print

A corner bulge is a problem most 3D printing enthusiasts encounter. Also known as a round corner or a corner swell, it can make your output less than perfect. Fortunately for you, there are a lot of things you could do to avoid such a problem. 

Here are ways you can prevent bulging corners on a 3D print:

1. Lower print speed.
2. Apply the maximum jerk speed.
3. Calibrate the print bed and Z offset.
4. Make the corner thicker.
5. Use a cooling system.
6. Try another type of filament. 

Read on below to learn more about how you could minimize these corner swells.

1. Lower Print Speed

Over-extrusion happens when the printer uses more plastic than the software expects. Because more material is produced, a bulging corner (among many other problems) occurs. 

One way to prevent this is to turn down your printer’s speed. This will avoid a lot of newly-heated filament from being extruded in a short amount of time.

This happens because the layer before the newly-heated filament hadn’t had enough time to cool down. 

As a result, the layer on top of it remains soft. More filament material is extruded, which then results in rounded corners. 

To avoid this problem, you can start by slowing the print speed. An adjustment of 30 to 40 mm/s should do. 

A slower print speed won’t only prevent bulging, but it can also lead to: 

• More robust and more durable product
• Smoother layer lines 
• Near-perfect print – it’s like looking at your sliced model

2. Apply the Maximum Jerk Speed

Apart from over-extrusion, printers cause bulging when the nozzle completely stops at the corner.

Slowing the printer speed too much may worsen the output. Because it has extra time on the corner spot, it’ll extrude more material that forms a bulging corner. 

On the other hand, it’s not good to accelerate the printer so much either. Doing so can lead to ringing, where vibration-caused waves appear at the corner. 

If slowing the printer doesn’t fix the bulge, apply the maximum jerk speed (measured as mm/s) instead. It’s the top speed that the printer can perform for instantaneous acceleration and deceleration. 

By applying the maximum jerk speed option, the printer doesn’t decelerate to zero. As a result, the corners will remain sharp and not bulging. 

Another good thing about the maximum jerk speed is that it stops the printer from running full speed. So apart from preventing rounding, you can avoid corner ringing as well. 

3. Calibrate the Print Bed and Z-Offset

Your uncalibrated print bed and Z offset may be another reason why you come up with rounded corners.

If these parts aren’t aligned, the printer will fail to extrude material evenly. As a result, the corners can end up more rounded – if not rough. Likewise, an unleveled bed can lead to a variety of other issues. 

The good news is that you can easily avoid such a problem. 

Printer Bed

Before you start printer bed leveling, you’ll need to prepare the following materials: 

• Paper
• Screwdriver or hex key
• Clean cotton or brass brush
• Razorblade or spatula
• Dish soap
• Clean, dry cloth
• Alcohol
• Heat-resistant gloves

First things first: you need to clean the nozzle with a dry, clean cloth. 

The same goes for the build surface, which you can clean with a razor blade or spatula. Once you’ve removed the dirt, you may wash it with dish soap. 

In case your printer doesn’t have an automatic leveling feature, you can do this manually by following these steps: 

1. Position the printhead. Set it to 0,0,0. 
2. Move the print head to the corner. Place the paper in between the nozzle and the bed. If there’s no resistance, tighten the gap. Make sure to do this on all five points. 
3. Check the leveling by printing the first layer. The entire layer should look the same. There should be no rounded corners. If issues remain, you may need to level the bed again. 

Z-Offset

Calibrating the Z offset helps you finetune the layers for no-bulge corner printing. 

You may do this two ways:

• Adjust the G-code. Home the printer at G28 Z0, then proceed with G92 Z0.1 to create a 0.1 mm offset. If you want to raise the nozzle, make sure to set the Z to -0.1.
• Use a slicer. This is an easier way to adjust the Z offset since all you need to do is download the Cura program. Click on the icon ‘Z offset plugin’ and alter the figures as needed. 

Make the Corner Thicker

Thinner outputs, like the feet of a small table, have higher chances of developing round edges. That said, you may avoid this by printing thicker feet. 

In case you need to stick with the thinner dimensions, make sure to give the product enough time to cool down, which brings me to the next tip. 

Use a Cooling System

As mentioned, if your print doesn’t have enough time to cool down, it could end up with swollen corners. 

As such, it’ll help to use a cooling system for your 3D printer. This will help solidify the product faster, thus keeping its sharper, more defined edges.

Here are some ways to help cool your prints quickly: 

• Increase the fan speed by manipulating the slicer settings.
• Use a stronger fan.
• Install a fan duct that will channel cool air towards the 3D printed model. 

Try Another Type of Filament

Thermoplastic Polyurethane (TPU) and Thermoplastic Elastomer (TPE) are popular 3D printing materials. They stretch and bend easily, which makes them better than most filaments.

This characteristic, however, makes them likelier to produce bulging corners. Given the compressed material behind these filaments, they tend to ooze faster during corner slowdowns—the result: unsightly swells.

To prevent this from happening, use a stiffer filament such as polylactic acid. It can reduce the chances of bulging – as well as warping. More importantly, it’s environmentally friendly and biodegradable! 

Final Thoughts

Bulging corners can be frustrating, but you can easily avoid them. As long as you follow the tips above, you can achieve the sharp corners that you’ve always wanted.